1. Field of the Invention
The aspects of the present invention relate generally to the field of molded foams.
2. Description of the Related Art
Molded foam is one of the most common forms of packaging material used for the shipment of fragile items. Some examples of molded foams are expandable polystyrene (EPS), expandable polypropylene (EPP), and expandable polyethylene (EPE).
Molded foam is initially supplied to molders as a resin in the form of beads. The beads are loaded into a mold along with a blowing agent, such as pentane or carbon dioxide, which allow the beads to expand upon processing. Steam pressure is used to expand the beads into a shape determined by the mold and then force the beads to fuse together after expansion. The fused beads are then cooled to form a molded, closed-cell foam part.
The cushioning characteristic of the foam is based on the shape of the foam, the bead size, the bead processing conditions, and the quality of the bead fusion. Variations in these characteristics may cause the foam to fail acceptable quality standards, because foam that falls outside acceptable quality standards may not, for example, adequately protect products from damage when the foam is placed around these products.
The quality of the bead fusion strongly influences the strength characteristics of the foam. The degree of fusion or how much the beads have bonded during the molding process determines the quality of the bead fusion.
Currently, the most common method for determining bead fusion quality is a visual inspection. In order to inspect the core or middle of the molded foam piece, an inspector must break apart or cut the molded foam piece to visually inspect the bead fusion quality. As a result, the foam is rendered unusable. Currently, no known solutions exist to reliably and repeatedly test the quality of fused beads in a foam without destroying the foam.
Therefore, it would be advantageous to have a reliable, repeatable, and non-destructive method for testing the bead fusion quality in molded foams.